This is a program project application for sexually transmitted diseases research, the Bay Area STD Research Program. The project includes a Core support component and four research projects: Chlamydia studies; Mycoplasma studies; studies of gonococcal protein II; and studies of gonococcal pili. The core brings together clinical facilities (Reproductive Infectious Diseases, SFGH; Adolescent medicine STD, UCSF; City Clinic, San Francisco), existing clinically oriented research programs on Chlamydia, pelvic inflammatory disease, and gonococcal infection, and the STD Training Program, with basic science research facilities (Hybridoma Facility, U.C. Berkeley, Naval Biosciences Laboratory; Molecular genetics, Department of Medical Microbiology, Stanford; and Protein Chemistry Laboratory, Department of Medical Microbiology, Stanford). The integration of these research resources provides a very strong program with balance between clinical and basic science investigation. Each of the research projects will make use of the Core resources to develop data to improve the understanding of sexually transmitted diseases.